The objective of this project is to establish a Crystallography Core to produce accurate three-dimensional models relevant to the program of projects in Structure-Based CD4-gp120 Antagonism. This core will interact with all other components of the program and, in particular, will participate in the design of antagonists based on the crystallographic structures of relevant complexes. Thereby, the Crystallography Core will contribute to the effort to design therapeutics suitable for the management or prevention of AIDS. The specific aims of this scientific core are: (1) to analyze complexes of candidate small molecules with HIV-1 gp120, (2) to analyze complexes of candidate miniproteins with HIV-1 gp10, (3) to analyze complexes of the CD4 D1D2 fragment with drug- resistant gp120 variants, (4) to analyze other relevant complexes that might be developed, such as with D1D2, sCD4 or fragments of chemokine receptors, and (5) to design or improve upon compounds that will inhibit the CD4-gp120 interaction.